Quantifying and sustaining biodiversity in tropical agricultural landscapes

Abstract

Decision-makers increasingly seek scientific guidance on investing in nature, but biodiversity remains difficult to estimate across diverse landscapes. Here, we develop empirically based models for quantifying biodiversity across space. We focus on agricultural lands in the tropical forest biome, wherein lies the greatest potential to conserve or lose biodiversity. We explore two questions, drawing from empirical research oriented toward pioneering policies in Costa Rica. First, can remotely sensed tree cover serve as a reliable basis for improved estimation of biodiversity, from plots to regions? Second, how does tropical biodiversity change across the land-use gradient from native forest to deforested cropland and pasture? We report on understory plants, nonflying mammals, bats, birds, reptiles, and amphibians. Using data from 67,737 observations of 908 species, we test how tree cover influences biodiversity across space. First, we find that fine-scale mapping of tree cover predicts biodiversity within a taxon-specific radius (of 30-70 m) about a point in the landscape. Second, nearly 50% of the tree cover in our study region is embedded in countryside forest elements, small (typically 0.05-100 ha) clusters or strips of trees on private property. Third, most species use multiple habitat types, including crop fields and pastures (to which 15% of species are restricted), although some taxa depend on forest (57% of species are restricted to forest elements). Our findings are supported by comparisons of 90 studies across Latin America. They provide a basis for a planning tool that guides investments in tropical forest biodiversity similar to those for securing ecosystem services.conservation science | countryside biogeography | ecosystem services | extinctions | species-area relationship W hat is the potential of sustaining biodiversity and ecosystem services in agricultural landscapes? The future of biodiversity hinges on the answer, given the limited scope for expanding protected areas. Moreover, the generation and delivery of many vital ecosystem services occurs on local to regional scales in socialecological systems where people make their livelihoods through cropping, grazing, forestry, and other rural activities. The answer is incomplete, but appears to be "high" (e.g., refs. 1-3). A further question, however, is how can this potential for conservation into the Anthropocene can be realized, with land use, other dimensions of global change, and rates of extinction intensifying rapidly worldwide (4-6) and weak institutions for protecting the global commons (7)?Efforts to secure biodiversity and ecosystem services in rural landscapes are expanding and becoming more sophisticated (e.g., refs. 8 and 9). In the case of ecosystem services, both scientific and policy support for targeting investments have advanced rapidly (10, 11). In China, for example, 200 million people presently are being paid to engage in conservation and restoration activities; since 2000 these investments have resulted in many ecosystem servi...

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